Coherer Detector!! A very useful blast from the past, circa 1896. Yeah, that's over 100 years ago.
N-1896  $59.95

Order N-1896 .:| Here |:.

A brand new Marconi or Branley type Coherer detector designed from an 1896 original. Inside the tube are two 4mm machined brass electrodes with 15 degree faces. Each electrode is soldered to a special braided wire that has the same coefficient of expansion as the glass. Between the two electrodes are the metal filings, 95% Nickel with 5% Silver. There is a vacuum in the coherer tube and it is completely sealed.

When a miniscule RF (Radio Frequency) Voltage is placed across the electrodes, the nominal resistance between the electrodes will change from 100,000 Ohms down to as low as 10 Ohms, depending on the intensity of the signal.

The coherer tube will remain in the low resistance mode until it is gently tapped with a wooden stick or pencil. When tapped, the coherer goes back into the high resistance mode until another electrical disturbance is detected. The purpose of the coherer tube is to detect weak Radio Frequency signals. It is said that Marconi picked up three dots, the letter S, across the Atlantic Ocean in the early 1900s with a coherer tube.

This auction includes: 1 Coherer detector in a vacuum glass tub, 1 Spark Transmitter from a fire-place lighter, and 1 Digital Volt Meter.. Also included is a set of instructions with a historical perspective of the coherer detector. We constructed an original Marconi type receiver and had to make a coherer tube… So we machined a few extra parts… and sent them off to the glass company. Therefore we have a few extra Marconi type coherer detectors to sell.